Laser Micro-beam Manipulation System for Cells

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Mechanical and optical design for assembly of vascular endothelial cells using laser guidance and tweezers

Laser is applied to guide and tweeze the vascular endothelial cells for assembly. The system is composed of three modules: laser guidance, micro channels and laser tweezers. The micro channel includes the assembly area, main channel and branch channels. The optical module is equipped with laser source, beam splitter, reflectors and lenses. The endothelial cells are delivered to main channel and guided through branch channel to the assembly area by laser. The optical tweezers then move the cells to the proper position. The design of optical modules is conducted for the maximum capability of manipulating cells. The micro channel is designed based on fluid mechanics to minimize the fluidic disturbance to the cells in the assembly area, and is fabricated by photo lithography. Polystyrene micro beads and endothelial cells are successfully guided and tweezed by this approach. The associated escape velocity and dragging force are investigated.     

Manipulation on human red blood cells with femtosecond optical tweezers

Different types of femtosecond optical tweezers have become a powerful tool in the modern biological field. However, how to control the irregular targets, including biological cells, using femtosecond optical tweezers remains to be explored. In this study, human red blood cells (hRBCs) are manipulated with femtosecond optical tweezers, and their states under different laser powers are investigated. The results indicate that optical potential traps only can capture the edge of hRBCs under the laser power from 1.4 to 2.8 mW, while it can make hRBCs turn over with the laser power more than 2.8 roW. It is suggested that femtosecond optical tweezers could not only manipulate biological cells, but also subtly control its states by adjusting the laser power.     

测量平板玻璃折射率实验中激光散斑削减方法的探究

本文描述了以激光为光源测量平板玻璃折射率实验中成像场产生散斑的现象,并获得了一种简单有效的散斑削减方法.理论上激光经过漫散体后产生微光束干涉场,利用统计学的规律,总结出了散斑元之间对比度的影响因素.实验中,选取动-静毛玻璃对作为削减器件,利用静止漫散体增加入射光的粗糙程度,通过缓慢旋转的运动漫散体,可将散斑对比度降为4%左右,使干涉条纹清晰可见.     

Shaping super-Gaussian beam through digital micro-mirror device

We have set up a novel system for shaping the Gaussian laser beams into super-Gaussian beams.The digital micro-mirror device(DMD)is able to modulate the laser light spatially through binary-amplitude modulation mechanism.With DMD,the irradiance of the laser beam can be redistributed flexibly and various beams with different intensity distribution can be produced.A super-Gaussian beam has been successfully shaped from the Gaussian beam with the use of DMD.This technique will be widely applied in lithography,quantum emulation and holographic optical tweezers which require precise control of beam profile.     

小型化可调光镊设计

光镊利用强会聚激光对微粒产生的梯度力来捕获微粒,可以进行无损、远程操控,同时具有皮牛精度的测力特性,已经成为物理学、生命科学和胶体化学等研究领域中不可缺少的研究工具。光镊效应可以表现微小的光子动量和角动量,是物理学的重要教学工具。本文根据高斯光束传播和变换规律,设计具有稳定捕获性能的最小化光镊,并给出了典型参数。光镊系统由捕获激光、光束耦合系统、倒置生物显微镜和大数值孔径物镜组成,成像系统由物镜、摄影目镜和CCD相机组成。本光镊系统具有紧凑特性,同时通过保持物镜后瞳充满度来实现稳定捕获。在该最小光镊系统上,可以根据用户需求增加光镊阱位操控系统、刚度调节系统和其他辅助设备以满足不同操控要求,可以很好地满足科研和教学需求。     

双光子聚合多次快速扫描机制与小线宽研究

采用自由基浓度起伏理论并考虑光镊集聚效应,理论研究了飞秒激光双光子聚合多次快速扫描的线宽问题。根据双光子光聚合过程中自由基浓度随时间变化的关系,考虑光镊力及自由扩散效应对自由基分布的影响,得到了多次快速扫描加工线宽的表达式。研究了多次扫描过程中产生自由基浓度随扫描次数的变化、双光子聚合加工不同扫描次数下加工线宽随激光功率的变化、多次扫描过程中间隔时间对于加工线宽的影响。多次扫描的线宽表达式可以直接回归至单次扫描的一般公式,且理论结果与文献中实验加工线宽相吻合,两者误差在2%。控制扫描间隔时间,减少自由基的向外扩散运动以及被树脂材料内大分子猝灭,使得活性自由基的分布更为集中,可以获得更小的加工线宽。研究结果为飞秒激光双光子更小线宽加工的研究提供了新的思路,为飞秒激光多次快速扫描加工提供了理论依据。     

有限远共轭显微镜光镊设计和误差分析

光镊是研究单分子生物物理特性的独特工具, 因而光镊设备的研发是一个极为重要的课题. 本文根据矩阵光学, 对基于有限远共轭显微镜的光镊操控光路进行计算, 得出了阱位径向操控和轴向操控方程, 并分析了光束调控系统、 共焦系统后置透镜和耦合透镜安装位置误差及物镜轴向位置调整对光镊阱位径向及轴向操控精度的影响. 计算结果显示, 当物镜初级像面和耦合透镜像方焦面完全重合, 光束调控系统和耦合透镜的距离误差对阱位径向和轴向操控精度没有影响. 光镊系统元器件定位不准时, 基于无限远共轭显微镜光镊的阱位径向操控误差和轴向操控误差都小于基于有限远共轭显微镜光镊的阱位径向操控误差和轴向操控误差. 当光镊耦合透镜定位误差控制在小于10 mm时, 基于有限远共轭显微镜光镊的径向和轴向操控误差分别小于5.9%和11.4%, 有限远共轭显微镜仍然存在改造为光镊的价值.本文理论为基于有限远共轭显微镜的光镊设计、改造和操控提供理论和实验指导. 关键词： 光镊 光学设计 矩阵 误差     

飞秒光镊技术及其发展

激光捕获技术是利用光辐射力来捕捉、移动和操纵微粒的先进技术。飞秒光镊在实现粒子微纳操纵的同时还伴随着非线性现象的发生。阐述了飞秒光镊的模型和原理以及系统的各种结构形式,包括单光束梯度力光阱、贝塞耳光阱、双光束光纤光阱和冲击波光阱几种形式,并分析了每种形式的特点。     

基于数字微镜阵列光调制的激光防护系统

提出一种基于数字微镜阵列(DMD)的激光防护系统设计方案, 利用DMD的光调制作用减少强激光对光电成像设备的损坏.详细介绍了系统的工作原理、DMD及CCD的选型、投影光路和光学转换系统的设计, 运用相移莫尔法进行了图像像素的调校.模拟实验结果显示, 该系统可在不同光斑半径和光强的条件下成功识别激光光斑中心点的像素坐标和半径, 实现对光斑对应区域的微反射镜控制, 激光光强可衰减70%以上.     

人肝癌组织细胞的激光光镊拉曼光谱研究

激光光镊与拉曼光谱相结合形成的激光光镊拉曼光谱系统(LTRS)已用于分析生物组织标本,可对单个活细胞进行操控和光谱收集。从拉曼光谱特征峰位置、强度和线宽可得到有关细胞的组成、结构及细胞内物质相互作用的信息。文章应用LTRS系统,分析了来自人的恶性肝癌组织的不同病变部位标本,包括肝癌组织细胞、肝癌癌旁细胞和远离肝癌组织的肝脏正常的组织细胞,观察到了随肝癌的病变部位变化所出现的一些有趣的拉曼光谱峰的变化。正常的肝组织细胞在1 070和1 266 cm-1处的峰很明显,而肝癌和肝癌癌旁组织细胞的这两个峰则不明显,肝正常组织细胞的1 445 cm-1峰明显高于肝癌和肝癌癌旁组织细胞。已知1 070 cm-1峰代表脂类和核酸,1 266和1 445 cm-1峰代表脂类和蛋白。引起这些峰变化的物质很可能参与了肝癌的发生。上述初步研究结果表明：单细胞激光光镊拉曼光谱可以区分肝癌的不同病变部位,将是检测和分析肝癌组织标本的一种很好的方法。     

Optical tug-of-war tweezers:shaping light for dynamic control of bacterial cells(Invited Paper)

We design and demonstrate new types of optical tweezers with lateral pulling forces that allow full control of biological samples with complex geometric shapes.With appropriate beam shaping,the dual tug-of-war tweezers effectively hold and stretch elongated biological objects of different sizes,and the triangular tug-of-war tweezers with threefold rotational symmetry steadily hold asymmetric objects in the plane of observation and exert stretching forces along three directions.We successfully apply these tweezers to manipulate microparticles and bacterial cells in aqueous media.     

INCREASING TRANSVERSE STABILITY OF OPTICAL TWEEZERS BY USING DUAL-GAUSSIAN BEAM PROFILE

Trapping force was calculated with a homogeneous dielectric sphere model. Results indicate that the transverse trapping force of optical tweezers can be increased effectively through modifying laser beam profile while the axial stability of the system is still assured. This is quite important when optical tweezers are applied to the precise measurements for single biological molecule.     

激光捕获技术及其发展

激光捕获技术是利用光辐射力来捕捉、移动和操纵微粒的先进技术。光镊即单光束梯度力光阱是通过在高度会聚的激光束束腰附近所产生的极高的场强梯度来形成皮牛顿量级的力,可以三维地捕获和操纵微小粒子。阐述了激光捕获技术的模型和原理以及系统的基本结构;追踪了激光捕获技术的最新研究进展;介绍了非高斯型光阱、光纤光阱和全息光镊等几种特殊形式,并分析了每种形式的特点。展望了激光捕获技术的发展前景。     

Near-infrared Raman spectroscopy of single optically trapped biological cells

We report on the development and testing of a compact laser tweezers Raman spectroscopy (LTRS) system. The system combines optical trapping and near-infrared Raman spectroscopy for manipulation and identification of single biological cells in solution. A low-power diode laser at 785 nm was used for both trapping and excitation for Raman spectroscopy of the suspended microscopic particles. The design of the LTRS system provides high sensitivity and permits real-time spectroscopic measurements of the biological sample. The system was calibrated by use of polystyrene microbeads and tested on living blood cells and on both living and dead yeast cells. As expected, different images and Raman spectra were observed for the different cells. The LTRS system may provide a valuable tool for the study of fundamental cellular processes and the diagnosis of cellular disorders.     

CO2相干激光轮廓成像研究

本文以自制CO_2相干激光成像的实验系统,成功地实现了相干激光的彩色轮廓成像。     

超短脉冲激光微束对细胞作用的研究

本文详细地介绍了我们自己设计和安装的一个Nd:YAG超短脉冲激光微束系统,该系统分成二个部分:激光源和显微镜。由电光调Q非稳腔Nd:YAG激光倍频后得到355nm紫外光进入显微镜并由物镜聚焦。同时,这超短脉冲激光微束照射在细胞上并且在细胞上产生一个可以自恢复的小孔。在文中我们还讨论了超短脉冲激光微束与细胞之间作用效应及机理。     

Combined dielectrophoretic field cages and laser tweezers for electrorotation

Symmetric rotating octode field cages do not allow simultaneous particle trapping and electrorotation. Laser-trapped particles can stably be held in inhomogeneous rotating electric fields. Therefore, in a combination of laser tweezers and field-cage (electro-optical cage) dielectric single-particle spectroscopy (DSPS) of particles and cells can be carried out at low electric field strength. The electro-optical cage overcomes the limitation of low enough effective particle conductivity ensuring repelling dielectrophoretic forces in conventional field cages. At low power, forces in field cages and laser tweezers hardly interfere and can be used to calibrate each other. Received: 3 May 1999 / Revised version: 16 August 1999 / Published online: 27 October 1999     

大鼠的发炎白细胞的喇曼光谱研究

为了研究大鼠处于正常状态和发炎状态下白细胞内部的物质是否发生变化,制备了35%总体表面积Ⅲ度烫伤导致全身炎症的模型,采用一个激发波长为780 nm的半导体激光束来囚禁和激发正常与发炎两种状态下单个白细胞的喇曼光谱.结果显示,正常状态和发炎状态下的白细胞喇曼光谱有显著的区别,主要在726、785、935、1093、1371和1657 cm~(-1)处发炎白细胞的峰值强度比正常白细胞明显高出很多;通过光谱指认表明,当机体发炎时,白细胞中的蛋白质氨基酸含量基本没有变化,但是蛋白质结构发生明显改变;核酸的碱基含量增加,DNA双螺旋结构发生改变.利用PCA主成份对单个白细胞的喇曼光谱进行分析,发现通过PCA可以完全区分出正常状态和发炎状态的白细胞.